Parallel straightedge



1937- 1.. H.'KL|TSCHE PARALLEL STRAIGHTEDGE Filed March 30, 1936 "FIG.

INVENTOF? Leo H. KHrsche BY 340W ATTORNEY Patented Dec. 14, 1937 2,102,008- PARALLEL STRAIGHTEDGE Leo H. Klitsche, Los Angeles, Calif., assignor to The A. Lietz Company, San Francisco, Calif., a corporation of California Application March 30, 1936, Serial No. 71,676

6 Claims.

This invention relates to a parallel straight edge, such-asused on drafting boards or the like.

The straight edge, as distinguished from a T- square of universal use, often employs a wire or twine', arranged near the edges ofthe board, for

guiding the straight edge in its movement along the drafting board. Such wire or twine arrangements usually employ a series of pulleys fixed to the board.

'I'he manner of passing the flexible element (the .wire or twine) around the pulleys and of attachingthe straightedge has been suchthat the "movement ofthe straight edge inevitably causes amovementof the flexible element. There "is also a :probability that the -straight edge will not be maintained in truly parallel positions, due "to stretch or shrink of the element.

' "It is iniigeneral one of the objects of this inventiontto. improve'such parallel straight edge devices.

It is another object of this invention to provide -a simpletand effective parallel straight edgethat "is. inexpensive: and that obviates the disadvantagkessabovenoted,

Thiswinizention possesses many other advantages, andhasother'objects which may be made more easily apparent'from a considerationof one embodiment. of the invention. For this purpose there is rshown atom in the drawing-accompanyingyandrrforming part of the present specification. This form shall now be described in detai1,,i1lust-rating thefigeneral principles of the invention; butiyit is to be understood that this detailed description 'is not-to be takenin a limsitingwsense since thescope of this invention is best defined; byyth'erappended; claims.

Referring to the drawing: Figure 1.is aplanview of a straight edge incorporating the invention shown. as installed on 4.0=,a drafting, board,' some of the parts of the straight edge being indicatedjin dottedlines;

Fig. 2 is an enlarged sectional view taken along the plane.2-2 of Fig. 1, but with' some parts of the board broken away, to reduce the size of the figure; and r Fig. 3 is a diagramillustrating the manner in which certainlelements of the straight edge device are assembled.

The drafting board I is shown as carrying the straight edge 2. This-straight edge may be made of any appropriate material, such as wood.

The motion of the straight edge 2 along the as indicated at 6 and 1, to the lower edge of the board I. I

The straight edge 2 carries a channel shaped metal member 8 having the flanges 9 and ill, by the aid of which this member 8 can'be attached permanently to the straight edge 2. For this 'purposa'hollow rivets l I can be used. This memher 8 forms with the straight edge a hollow housing throughwhich certain portions of the flexible elements 3and 4 extend, as will be hereinafter described. The member 8supports, adjacent each of its extremities 22 and 23, pulley structures l2, l3. The' axis of each of the pulley structures is formed by the aid of a stationary pin M. This pin as shown most clearly in Fig. 2, has an axis normal to the plane of the straight edge and extends throughan aperture in the member 8, that is formed by the inturned flange l5. The pin Hi can be so riveted over as to support the inner race 16 of a ball bearing structure for rotatably supporting the pulley proper I7. This-pulleyproper I1 is provided withan outer ball race l8; and a series of balls 19 are interposed between the inner and :outer races Hi and I8 to provide free rota- -tion oflthe pulleys. Each of the pulleys is furthermore provided with a pair of annulargrooves 20 and 2! in which the flexibleelements 3 and 4 are accommodated TheLends .22 and 23' of the channel dean, if desired,rhave:downward extensions 24, 25 through which a fasteningmeans', such as a hollow rivet, can be passed F The manner in which the flexible element ,3-,4-5 .is looped through the pulley structures will now 'be described, especially in relation to Fig.3. .One'en'd of the part 3 is fastened to the edge of the board I as by member 6, and extends upwardly'around pulley I! in a counterclockwise :direction. The element then crosses to the left hand. pulley l1" where it passes overthe pulley in a clockwise direction. Thence the flexible element. passes upwardly andrthrough an eye 26 and along the topedge of the board to the tension spring 5.v The other .part .4 of the flexible element extends from the tension spring 5 along the top edge of: the board I, through the eye 21, and then downwardly andaround pulley structure I? in a :clockwise direction. Then it crosses over the board I and passes around pulley structure I! in a counterclockwise direction. It thence passes parentithat: the pulley structure I! will rotatein .-'.a.; counterclockwise :direction, and pulley structure l'l' will rotate in a clockwise direction. The portions 3 and 4 cross between the two pulley structures. .Any variation in the position of the straight edge 2 in moving up and down the board ,ldoes not require any change in the length of {the flexible element 3-45. This is apparent because as the pulley structures I! and I1 move up and down with the straight edge 2, they merely act to rotate these pulley structures.

The tension spring 5 keeps the parts 3 and 4 of the flexible elements under tension at all times. Any stretch or shrinkage merely results in a compression or extension of the spring 5 without causing any tilting of the straight edge. Furthermore, it is possible to hold one end of the straight edge rigidly and the other end can be swung so as to set the straight edge at an oblique angle, as illustrated by the dotted line positions.

It can then be moved up and down the board at the new position.

Referring to Fig. 3, if pulley I 1 is shifted downwardly to give the straight edge an inclination downward toward the right, the right hand portion of element 4 will be pulled downwardly and the right hand portion of element 3 tends to become slack. However, as elements 3 and, 4 are connected at the top of the board and are slidable in eyelets 26, 21, the downward'pull on part 4 takes up the slack in part 3 and no looseness actually occurs, the spring merely shifting to the right.

Thus if the straight edge is set at the inclination indicated by A, the spring 5 will be shifted to the position marked 5A. Similarly, for inclination B of the straight edge the spring will assume the position 5B. These oblique positions slightly change the required overall length of the flexible element 3-4-5; but this is taken care of by the spring 5.

Once the straight edge 2 is thus set for any angle within limits, it is restrained against any change in its angular setting. This is due to the fact that each pulley structure I! or I1 is confined by parts 3 and 4 against any motion except one of rotation.

What is claimed is:

1. In a device of the character described, a straight edge member, a pair of pulley structures respectively supported adjacent opposite ends of the member, each pulley structure having a double groove, and a flexible element flxed at its ends, and adapted to be supported on a board, and passing around the pulleys in this order: from one end, around one groove of one pulley, then around one groove of the other pulley, then to the opposite edge of the board from. the fixed end, and then to the other groove of the first pulley, then to the other groove of the other pulley, and thence to the otherend, fixed adjacent the same edge of the board as the first end, the direction of the element around the pulleys being such that those portions of the element passing between the pulleys, cross each other, saidrelement being adapted to confine the straight edge to movement in parallel adjusted positions when maintained at a constant length, and means included in said element to permit variations in length, whereby the inclination of the straight edge may be adjusted,

2. In a device of the character "described, a

-flexible element having two parts and a tension spring joining the two parts, onefend of each part being adapted to be joined adjacent one edge of a board, each part crossing the board and then passing toward the opposite edge of the board, and a straight edge member having pulley structures guiding the flexible element, the element being so guided by the pulleys that par allel movement of the straight edge causes rotation of the pulleys without necessitating a change in length of the element, the tension spring permitting changes in the length of the element in response to adjustments in the inclination of the straight edge.

3. In combination with a straight edge adapted to be used with a drawing board, means for maintaining the straight edge in parallel adjusted position as it traverses the board, including a pulley rotatably supported near each end of the straight edge, a flexible resilient guiding element having its ends fixed near one edge of the board and passing around the pulleys in thisorder; from one end, around one groove of one pulley, then around one groove to the other pulley, then to the opposite edge of the board from the fixed end, thence along said opposite edge, and then to the other groove of the first pulley, then to the other groove of the other pulley and then to the other fixed end, the direction of the element around the pulleys being such that those portions of the element passing between the pulleys, cross each other, said element being slidably secured to said other edge whereby the inclination of said straight edge relative to said edge may be varied without disconnecting the element.

4. The combination of claim 3, wherein the resilient flexible guiding member is formed of two substantially non-resilient members joined by a tension spring adjacent the opposite edge of the board.

5. In combination with a straight edge adapted to be used with a drawing board, means for maintaining the straight edge in parallel adjusted position as it traverses the board, including a pulley rotatably supported near each end of the straight edge, a pair of flexible guiding elements having one end of each fixed near one edge of the board and passing around and. between the pulleys to the opposite edge of the board, so that as the straight edge is moved, the pulleys are caused to rotate in opposite directions without changing the combined length of said elements, means slidably securing the elements to said opposite edge, means connecting the ends together adjacent said edge, said means being adapted to maintain a constant tension in the elements, whereby the combined length of the elements can be varied to permit substantial alterations in the inclination of the straight edge relative to the edge of said board.

6. In combination with a straight edge adapted to be used with a drawing board, means for maintaining the straight edge in parallel adjusted position as it traverses the board, including a pair of pulley structures respectively supported adjacent opposite ends of the member, a flexible guiding element fixed at its ends and passing around the pulley structures so as to guide the straight edge in parallel adjusted position without change in length, and means to permit variations in length of said element, whereby the inclination of the adjusted position of the straight edge may be altered.

LEO H. KLITSCHE. 

